Although substantial efforts have been made in the chain saw art to develop integrated handle and vibration isolation systems for the purpose of reducing operator fatigue, the effort to optimize the reduction of chain saw vibration, while facilitating overall handling and control, has been continuing in nature.
Substantial advances in the vibration isolation art have been effected through contributions by the assignee of the present invention, as evidenced by the following U.S. Pat. Nos.:
______________________________________ Frederickson et al 3,542,095 (November 24, 1970) Frederickson et al 3,652,074 (March 28, 1972) Frederickson et al 3,698,455 (October 17, 1972) Frederickson et al 3,813,776 (June 4, 1974) Bailey 3,845,557 (November 5, 1974) Bailey 3,911,580 (October 14, 1975) Bailey 3,972,119 (August 3, 1976) Thompson 4,041,606 (August 16, 1977) ______________________________________
Other efforts in the chain saw vibration isolation art, as provided by other practisioners, are generally evidenced by the following U.S. Pat. Nos.:
______________________________________ La Force 3,140,746 (July 14, 1964) Dobbertin et al 3,224,473 (December 21, 1965) Irgens 3,372,718 (March 12, 1968) Rauh 3,409,056 (November 5, 1968) Kobayashi 3,525,372 (August 25, 1970) Scharpf 3,530,909 (September 29, 1970) Sherwood, Jr. et al 3,637,029 (January 25, 1972) Stihl et al 3,651,839 (March 18, 1972) Emmerich et al 3,680,608 (August 1, 1972) Kobayashi et al 3,700,015 (October 24, 1972) Makinson et al 3,728,793 (April 24, 1973) Notaras et al 3,733,700 (May 22, 1973) Heermann 3,772,784 (November 20, 1973) Schulin 3,845,827 (November 5, 1974) Kolorz 3,849,883 (November 26, 1974) Dillon 3,889,763 (June 17, 1975) Nagashima et al 3,945,119 (March 23, 1976) ______________________________________
Although the foregoing listing of patents is believed to provide a generally reasonable assessment of prior art efforts, it is to be recognized that the compilation set forth above does not constitute a complete delineation of each and every prior art effort in the vibration isolation art.
The present invention is directed toward a furtherance of the continuing efforts to improve chain saw handling characteristics by uniquely integrating a housing arrangement for vibration isolating means with a particular efficaciously arranged front hand grip. This front hand grip constitutes a generally U-shaped hand grip portion which is incorporated in a front handle of a chain saw and extends transversely across a longitudinal median plane of a guide bar. The U-shaped hand grip portion uniquely cooperates with a forward portion of a rear handle so as to define a mounting for a vibration isolation unit.
The unitized, i.e., interconnected, front and rear handles of the handle assembly of the invention are mounted on oppositely axially directed mounting shafts and cooperate with axially oppositely directed abutment means so as to affirmatively impede axially oppositely directed movements of the vibration generating assembly of the chain saw relative to the handle suspension system.
A typical chain saw with which the present improved suspension system is incorporated comprises a vibration generating assembly including engine means, with guide bar means extending generally longitudinally from one side portion of the chain saw and having a longitudinal median plane and a longitudinal median axes. In the upright cutting configuration of the chain saw, the longitudinal median plane would be generally vertically oriented, with the longitudinal median axis extending in the longitudinal median plane, generally horizontally.
The vibration generating assembly would further typically include cutter chain means mounted on the periphery of the guide bar means for movement thereabout, with drive means being operable to drivingly couple the engine means with the cutter chain means.
Basic aspects of the suspension system, improved through the present invention, include means operable to yieldably support the vibration generating assembly and comprising a handle assembly and vibration isolating means. The handle assembly would typically include a front handle and a rear handle both having a hand grip portion. The vibration isolating means would serve to interconnect the handle assembly and the vibration generating assembly.
The improvement in the suspension system, afforded through the present invention, comprises first and second axially oppositely directed mounting shaft means located on one side of the longitudinal median plane of the guide bar means. These mounting shaft means are operable to provide force transmission between the vibration generating assembly and the suspension system and are oriented with their longitudinal axis extending generally longitudinally of the longitudinal median plane of the guide bar means.
A first cushioning means, included in the vibration isolating means, may comprise first, resilient diaphragm means having a first aperture extending generally transversely of the longitudinal median plane of the guide bar means. The first mounting shaft means passes through a first aperture of this first diaphragm means, with the first diaphragm means being mounted upon the first mounting shaft means. A first resilient impedance means, mounted on the first mounting shaft means, engages one side of the first diaphragm means. A second resilient impedance means, mounted on the first mounting shaft means, engages an opposite sides of the first diaphragm means. Mounting means interconnect the first diaphragm means, in a vibration isolating condition, between the vibration generating assembly and the suspension system.
Second cushioning means are also included in the vibration isolating means and may comprise second, resilient diaphragm means having a second aperture extending generally transversely of the longitudinal median plane of the guide bar means. The second mounting shaft means passes through a second aperture of the second diaphragm means, with the second diaphragm means being mounted upon the second mounting shaft means. A third resilient impedance means is mounted on the second mounting shaft means and engages one side of the second diaphragm means. A fourth resilient impedance means is mounted on the second mounting shaft means and engages in opposite side of the second diaphragm means.
Another mounting means connects the second mounting shaft means in a vibration isolating condition between the vibration generating assembly and the suspension system.
A unique U-shaped hand grip means, included in the improved suspension system, extends transversely of the longitudinal median plane of the guide bar means and is provided with a pair of leg portions extending above the engine means.
One of these leg portions extends from a forward end of the rear handle, generally transversely across the longitudinal median plane of the guide bar means. The other of the leg portions is spaced generally above the one leg portion, with a generally upright connecting portion serving to interconnect the one and other leg portions.
The U-shaped hand grip means extends transversely across the longitudinal median plane of the guide bar means and is located generally above the vibration generating assembly.
Another independently significant aspect of the invention resides in that portion of the improved suspension system noted above which is characterized by the unique U-shaped hand grip means incorporated in the front handle, as above noted, and which intersects the longitudinal median plane of the guide bar means, above the engine means. This arrangement provides a front hand grip portion directly in front of, but located above, the rear hand grip portion of the integrated handle assembly. In this structure, a vibration isolating or "cushioning" means serves to interconnect the U-shaped hand grip portion and the vibration generating assembly of the chain saw.
Other aspects of the invention which are deemed to be significant, either individually or collectively, in the context of either of the basic aspects of the invention noted above should also be considered.
One such combination aspect pertains to a chain saw, as above described, wherein each of the first and second axially oppositely directed mounting shafts have a longitudinal shaft axis, with the longitudinal axes of the first and second mounting shafts being mutually parallel and coplanar.
In this arrangement, the first and second axially oppositely directed mounting shafts are mounted, respectively, on first and second, suspension system restraining, abutment means. The first and second suspension system restraining abutment means are carried by the vibration generating assembly and are operable to limit longitudinal movement of the handle assembly in opposite directions, longitudinally of the chain saw.
Another combination concept resides in a chain saw as above described wherein the rear handle includes rear handle end means facing the front handle and the front handle includes front handle end means facing the rear handle end means. Recess means, carried by at least one of the front and rear handle end means serves to house and restrain at least a portion of a vibration isolating or "cushioning" unit.
In describing the invention, reference will be made to appended drawings which illustrate, by way of example but not by way of limitation, a presently preferred embodiment of the invention.